Just curious,

What kind of HP will I gain on my 305 if I change the TBI to TPI?

Another thought is to change the crank and get it to a 350 (345), or so I have heard that this is a possibility.

My engine is still being looked up to find out how it was setup.

I already have the complete TPI setup off of a 91 Z.

Thanks

Rob
92 RS
305
Manual

 

The crank size is the same for 305's and 350's. Its the bore size that is different, and the 305 and 350 blocks are different. You cannot turn a 305 into a 350. Your option is to remove the 305 block and replace it with a 350 one.

My dad converted his 305 TBI over to TPI, and he gained 17 horsepower and 70 torque at the rear wheels. Then he swapped in a 350 engine and has never been happier. Yes its very much worth it to dump TBI and switch to TPI or better fuel injection.

 

Hey, sorry to go off topic, but I am wanting to do the exact same swap, and I am just wondering if you have a list of everything I would need to do the entire swap from TBI to TPI. Would I need and sensors and what kind of ecm, any info would be great. I have the L03 right now and would love the better power and economy the TPI has to offer.
Thanks
Lc

 

https://www.thirdgen.org/newdesign/tech/tbitotpi.shtml

 

Before you spedn a lot of dough on a TPI unit you m ight wanna look at the holley stealth ram.

-- Joe

 

Here you go. Can't argue with actual dyno graphs. Looks like to me you should concentrate on exhaust before anything else. Maybe do the ultimate tbi mods and you will be a lot more happier than if you switched to tpi.

http://bitchincamaro.no-ip.com/dyno.html

 

I think the TPI swap is still valid. And a stock 350 doesn't gain a whole lot with an aftermarket unit like the Stealth Ram. It's when you really start getting into headwork and cam that the change is worthwhile.

Even if he installs the TPI system now. He can still upgrade to the Stealth Ram later. Just change the intake, plenum and runners.
TPI system's are pretty inexpensive all things considered. If you already own the TPI hardware it's definatley worth while.
I think it's worth it. Go for it.

 

I remember someone on the boards saying there dad had a 91 (i think) lo3 car. He gained 17hp and 70lbs torque at the wheels from just a TPI swap and nothing else.

If he sees this post im sure he will confirm this.

 

Uhh... yes. I posted the second post in this thread.

 

Thanks all.

For those that have done this,.. is it straight forward?

I have spoke with some companys that sell TPI's setup's and they say it is a straight swap.

I spoke with Howell and they say to convert the TBI harness, so that all of my guages work.

I thought that the wiring was all the same (under the dash) except the fuel injector part.

I have the harness,.. straight forward?

Rob

 

No. The power gain is not worth the time/money - you could go faster for cheaper by slaaping on a good used carb and intake. However, the increased flexability and near limitless tunability you would gain from converting to fuel injection make the swap worth its weight in gold. Do the swap, read TRAXION's article on PROM burning (a sticky at the top of the DIY PROM board), learn to burn your own chips, and your TPI (I consider your setup TPI if you are using GM's 730 or 749 ECM) will totally knock your socks off. Good Luck.

Kyle

 

Like I said, you can't argue with ACTUAL DYNO GRAPHS. If you look at his graphs from his swap, which includes other mods such as aluminum driveshaft, underdrive pulleys, airfoil, and cold air intake, you will see that he gained a combined 9 hp and 39 ft torque, all while moving the hp peak down and the torque peak up, exactly what you don't want to do.

 

WHOOOPS LOL.

I didn't read anything besides his first post LOL. Im lazy.

 

I did a little different conversion I went from an LG4 to the TPI on my 87 Formula, and I really think it was worth it.

I remember swapping the following:
engine wire harness
dash wire harness (I think you can skip this one with TPI)
intake runners etc.
Swapped sides with the Battery
Ran the fuel lines
Dropped the axel, put in the TPI fuel pump in tank.

I really did not notice a big gain with the HP end, not until I got into programming, but my fuel milage wendt from 17mpg to 23mpg


John

 

If you want more hp full exhaust is the way to go as far as first mods. If you already have a tpi setup go ahead and do it. I love the torque and the car runs much smoother. I dont regreat doing the swap though.

 

One advantage you will get for doing a swap... is experience. well worth it. I am MUCH more comfortable working on computer controlled GM vehicles. I would be that once you get done, you will be more knowledgable than many if not most of the other folks here.

John